Phytotoxicity of aluminium-fluoride complexes and their uptake from solution culture by Avena sativa and Lycopersicon esculentum
Date
1997
Authors
Stevens, D.
McLaughlin, M.
Alston, A.
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Advisors
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Journal article
Citation
Plant and Soil, 1997; 192(1):81-93
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Abstract
Avena sativa (oats) and Lycopersicon esculentum (tomatoes) were grown in dilute nutrient solutions supplemented with Al only, F only or a combination of both. In solutions containing Al and F, shoot growth was limited when predicted Al(r). (Al<sup>3+</sup>, AlOH<sup>2+</sup> and Al(OH)<inf>2</inf>/<sup>+</sup>) activities were < 0.1 μM, activities three orders of magnitude lower than the critical value determined with Al only. The data suggest that at the activities used in these experiments, Al(r) is most toxic, AlF<sup>2+</sup> and AlF<inf>2</inf>/<sup>+</sup> are toxic to a lesser extent, and AlF<inf>3</inf>, AlF<inf>4</inf>/<sup>-</sup> and F<sup>-</sup> are least toxic. Fluoride concentrations in shoots grown in solutions correlated best with positively charged AlF(x)/(3-x) species (i.e. AlF<sup>2+</sup>, AlF<sup>2+</sup>) and the molar ratio of F:Al in most plants shoots was about 3:2. However, when activities of positively charged AlF(x)/(3-x) species were low (< 50 μM) and the activity of AlF<inf>3</inf> species high (500 μM) the molar ratio of F:Al in plant shoots suggested AlF<inf>3</inf> was taken up. These findings are discussed in relation to plant uptake and toxicity. Measured concentrations of Al(r) and F<sup>-</sup> in solutions containing Al and F were compared with concentrations predicted by a computer model (GEOCHEM-PC). The method for measuring F<sup>-</sup> concentrations, using a non-complexing buffer and F ion-selective electrode, gave good agreement with predicted F<sup>-</sup> concentrations. The 8-hydroxyquinoline method for measuring Al(r) concentrations did not agree with predicted concentrations, highlighting the limitations of this method when measuring Al(r) in the presence of F in a multi-ligand system with high concentrations of F and Al.